Canto wanted to give the ­children of Rocinha an alternative to joining the drugs gangs that ruled the slum.

He knew the state education system was failing them ­miserably so he employed a couple of teachers to try to fill a few of the gaps.

Canto told me seven years ago he thought Arthur had the potential to thrive if he could go to a decent school.

And so, later that year, the Daily Mirror paid for him to attend a school in Barra, to the south-west of the city, away from the gunfire, for 12 months.

The next year, Craig Bellamy and Kieron Dyer took up the reins and paid Arthur’s school fees.

The year after that, he began doing so well that the school decided they would give him a scholarship.

And when I sat with him in the hotel bar on Sunday evening, he told me – in good English – he had finished his end-of-year exams earlier that day.

I know from his teachers that he has turned into an A-student. Now he is hoping to get the grades to go to university in Rio in March next year.

Beyond that? Well, huge oil reserves have been discovered off Rio’s coast. Arthur’s dream is to become a petroleum engineer. He will be in demand.

We walked back to Rocinha, to the tiny one-bedroom apartment he shares with his mother and sister above an alleyway off the Via Apia.

Arthur’s mother was wearing a woolly hat. She has cancer. She has worked in a cafe in the centre of the city for almost 20 years and her employer is paying for her treatment.

Arthur and his mother talked about the changes that have happened in Rocinha in the ­build-up to this summer's World Cup.

As part of the preparations for the tournament, Rocinha was “pacified” by the Unidade de Policia Pacificadora, which re-established police authority in the favelas.

On our way into Rocinha, we had walked past a group of armed police heading in the other ­direction.

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Rising up: Arthur says Rocinha has become a "much, much better" place to live

“It is good to see the police here now,” Arthur said. “A few years ago, that would not have happened. This is a new Rocinha. It is not just a place of gunshots and violence. There are hospitals and more schools. It is a much, much better place to live.”

But even though winning the right to host the World Cup has brought improvements to Rocinha, Arthur understands why there have been protests, too.

Arthur is a Flamengo fan. Like most 17-year-old Brazilian lads, he is almost beside himself with excitement about the World Cup.

He is optimistic about Brazil’s chances, he says. And he’s confident that his favourite player, Neymar, can help his country win the tournament for the sixth time.

But in a way, Arthur embodies the reasons why there has been so much fury about the ­corruption and the waste that has already tainted this ­tournament.

Like his country, there was a time not long ago when Arthur did not allow himself to dream. But those days have gone. ­Brazilians expect better now.

Four years ago, The Economist devoted its front cover to an image of the statue of Christ on ­Corcovado mountain above Rio zooming into the sky like a rocket.

“Brazil takes off,” the headline said.

The country seemed set for a place at the top table of nations.

The World Cup was supposed to confirm the emergence of the new Brazil. Instead, it has shone a bright light on the corruption that infects the country.

Money spent on stadia has spiralled out of control, promised improvements to the country’s transport infrastructure have failed to materialise.

“The story here in Brazil is about the ­aspirations of a new generation,” former Globo journalist Eduardo Mack said.

Brazilians have a different view of their place in the world now but it jars with the grinding poverty and lack of public amenities they see around them.

“In a country of misery,” a banner strung up on Copacabana beach read yesterday, “a World Cup financed by public money is a moral problem”.

It is a common feeling.

“I put a picture up on Instagram a couple of weeks ago,” Canto said, “that was just saying, ‘Let’s go, Brazil’. I got all these replies back saying, ‘But we need better hospitals, we need better schools’.”

I said goodbye to Arthur and wandered back through the alleyways of Rocinha with their bars and their arcade games and their ­hairdressers.

One day, when he’s a qualified petroleum engineer, maybe he’ll be able to move out of the favela.

The World Cup, for all the ­darkness it has exposed – perhaps because of the darkness it has exposed – is acting as a catalyst for change in Brazil.

Arthur’s generation will have to carry the fight forward. Before I left and he clanged shut the steel door to his apartment, he smiled when I mentioned the protests again.